This paper studies the law of the effect of the VAE redispersible emulsion powder content on the tensile properties of polymermodified cement based composed joint sealant (PCJS) systematically by single factor test. A new kind of PCJS is produced by adding VAE redispersible emulsion powder into styreneacrylic emulsion based cement compound joint sealant. Under condition of different polymer powder content, the tensile strength, early tensile strength, tensile breaking elongation, peak strain and tensile modulus of PCJS are measured respectively. Moreover, the tension failure modes of the PCJS with different content of VAE redispersible emulsion powder are recorded and investigated. The effect of different cure condition and emulsion powder content on early tensile strength of PCJS is studied. The composite effect of styreneacrylic emulsion (SAE) and VAE redispersible emulsion powder on the modification of PCJS is studied. The results show that no obvious differences in materials early tensile strength emerge at the temperature variation of 30o C. The tests on specimens with full curing date of 28 days show that as the added proportion of VAE redispersible emulsion powder increases, significant growth in both PCJSs tensile strength and tensile modulus can be observed. In addition, the tensile failure mode is transformed from cohesive failure to adhesive failure with the increase of polymer powder content. Besides, the tensile deformation capacity of PCJS increases first and then decreases along with the increasing of the VAE redispersible emulsion powder content. Besides, the PCJS can optimize the performance of tensile deformation, as the VAE redispersible emulsion powder is added into it by 2%~3%.